SCI0: SCI0 Interpreter with added PKWare DCL Implode compression (comp_method=3)

[robbo007]

Hi guys,
On my quest to save hard disk space for my project after many hours of pulling my hair out I've managed to get a working version of the SCI0 Interpreter with added PKWare DCL Implode compression (comp_method=3) and only using a 6kb of memory footprint. Maybe someone else could do this better using less memory?

### Memory footprint (decompressor in SCIV.EXE)

4096-byte dictionary window : 4096 bytes
Fixed decode tables         : ~1800 bytes (compile-time constants)
State overhead              :  ~200 bytes
TOTAL                       : ~6096 bytes (~6KB)

I've also written a makevols.exe that compresses each resource with DCL Implode. Both are attached if anyone wants to test them.

[lskovlun]

How much of this memory footprint is in heap, and how much is in hunk?

[Kawa]

How much of this memory footprint is in heap, and how much is in hunk?

I don't think I understand the question. The decompressor is not itself a resource, and once uncompressed for use the resources are as big as always. Right?

[lskovlun]

How much of this memory footprint is in heap, and how much is in hunk?

I don't think I understand the question. The decompressor is not itself a resource, and once uncompressed for use the resources are as big as always. Right?

The buffers can be allocated near (= in the data segment, preventing that space from being used for the heap) or far (= hunk).

[robbo007]

Hi guys,
The patch costs the game zero heap and about 6KB of hunk, which matches how Sierra's own SCI16 engine handles this (it keeps the whole DCL work buffer in a far hunk Handle with zero near-heap use).
Hope that helps.

[cosmicr]

Pretty neat, what's the compression ratio like? Imagine if Police Quest 2 was on just one disk etc... that would have been a game changer (literally!) back in the day.

Are there any SCI0 games that push the limit of the hunk memory?

[lskovlun]

They almost certainly would have on some configurations. I think most SCI0 games required only 512KB of conventional memory? Not everyone had 640KB. And then there's various TSRs.
In fact these games also technically required an 8MHz processor, but I found that they ran passably on our 4.77MHz machine.

[cosmicr]

Yeah I could have sworn I played KQ4, PQ2 and CB on my Tandy 1000 with 256k ram. I might be misremembering.

[lskovlun]

They had this feature where you could monitor how much hunk was used at any given time. There was also a minHunk= directive in resource.cfg, which was checked on startup. Do some thorough playtesting, and you'll know what to set that value to.

EDIT: but apparently not in SCI0. Sigh, it's been too long since I worked on this.

[robbo007]

Pretty neat, what's the compression ratio like? Imagine if Police Quest 2 was on just one disk etc... that would have been a game changer (literally!) back in the day.

Are there any SCI0 games that push the limit of the hunk memory?

So here is a comparison with my game. Its at 7.66mb right now but I still have to add all the music resources. So I think I'll be hitting 9.5mb when finished. Way too big. LOL

Code: [Select]

┌──────────────────────────────────────────────────────────────┬────────────────────┬─────────────────────────┐
│                           Version                            │  Size (measured)   │         vs raw          │
├──────────────────────────────────────────────────────────────┼────────────────────┼─────────────────────────┤
│ Raw/uncompressed (game-o/RESOURCE.001)                       │ 7.66 MB (7.30 MiB) │ ?                       │
├──────────────────────────────────────────────────────────────┼────────────────────┼─────────────────────────┤
│ Original SCI0 LZW/Huffman (MAKEVOLS, doc figure)             │ ~5.20 MB           │ ~1.40:1 (28.6% smaller) │
├──────────────────────────────────────────────────────────────┼────────────────────┼─────────────────────────┤
│ New DCL Implode patch (compress/RESOURCE.001, current build) │ 3.91 MB (3.73 MiB) │ ~1.96:1 (48.9% smaller) │
└──────────────────────────────────────────────────────────────┴────────────────────┴─────────────────────────┘
I did achieve better compression using RAR on the raw/uncompressed resource file, but in my case I not only wanted to save space on floppy disks I also want to save space on the hard disk as some of the older systems have very small hard disks. So I think the payoff of loosing 5kb memory, less hard disk space and number of floppy disks is the "happy medium".